The removal of sulfur from fluid streams can be desirable or necessary for a variety of reasons. If the fluid stream is to be released as a waste stream, removal of sulfur from the fluid stream can be necessary to meet the sulfur emission requirements set by various air pollution control authorities. Such requirements are generally in the range of from about 10 ppm to 500 ppm of sulfur in the fluid stream. If the fluid stream is to be burned as a fuel, removal of sulfur from the fluid stream can be necessary to prevent environmental pollution. If the fluid stream is to be processed, removal of the sulfur is often necessary to prevent the poisoning of sulfur sensitive catalysts or to satisfy other process requirements.
Various absorption compositions have been used to remove sulfur from fluid streams when the sulfur is present as hydrogen sulfide. These absorption compositions can be, manufactured by a variety of methods which include extrusion production techniques. A problem that is often encountered in the production of these absorption compositions is equipment wear caused by the abrasive nature of the absorption materials being manufactured. In certain attempts to produce commercial quantities of absorbent compositions, excessive equipment wear and downtime caused by the abrasive characteristics of the absorption material components have, in effect, rendered the production of such compositions commercially unviable.
A further property of which it is desirable for absorption compositions to have is the ability to absorb large quantities of sulfur. This capability to absorb large amounts or concentrations of sulfur is sometimes referred to as "sulfur loading" and is generally reported in terms of percent sulfur loading. The term it percent sulfur loading" is generally defined as the parts by weight of sulfur absorbed upon the surface or within the pores of an absorption composition per parts by weight of the total absorbent composition multiplied by a factor of 100. It is desirable to have an absorption composition with the largest possible sulfur loading capacity.
An additional property desirable for an absorption composition is the ability to be regenerable to the original absorbing composition state after the absorbing composition bas become spent. An absorbing composition generally becomes spent when its sulfur loading capacity has essentially been used up. It is desirable for the absorbing composition to be able to undergo numerous regeneration cycles without losing its sulfur loading capacity and other desirable properties.
Even though many absorbing compositions can effectively absorb hydrogen sulfide from fluid streams containing hydrogen sulfide, it is not uncommon for many of these absorbing compositions to effectively oxidize significant amounts of hydrogen sulfide to sulfur dioxide when contacted with such fluid streams. The resulting sulfur dioxide is not removed from the fluid stream by the absorbent composition and thus passes through the absorbent material with the contacted fluid stream. This phenomena is sometimes called "sulfur slippage." It is desirable to have an absorption material which bas a high capacity to absorb sulfur from a fluid stream and which minimizes the amount of sulfur slippage.
In some absorption compositions, the addition of a promoter compound can be used to allow for easier regeneration of the absorbing material.